Hollow-core Beam Research Articles

Study on the flexural behaviours of precracked hollow core beams strengthened with core filling and unbonded prestressing steel strands

Extensive investigations show that the core-filling method can markedly improve the shear behaviour of hollow core beams (HCBs). However, few investigations were carried out to study the flexural behaviours of the HCBs strengthened with this method. In this study, the flexural behaviours were first studied, where the HCBs were strengthened with a hybrid strengthening method of the core-filling and external unbonded prestressing steel strands. Six types of HCB specimens were fabricated and investigated. The initial damage and prestress levels were selected as the main parameters. Before strengthening, the HCB specimens were loaded to 40.6 %, 66.3 % and 100 % of their ultimate load to pre-set some cracks in the concrete beams, which corresponded to the maximum crack widths of 0.2 mm, 0.4 mm and wider than 1.5 mm, respectively. Compared with the control beam, the strengthening with the core-filling improved the flexural load carrying capacity by 3.93 %, whereas the hybrid strengthening method improved by 33.67 %; the cracking loads for the two strengthening methods increased by 10.34 % and 128.28 %, respectively. Moreover, the experimental results showed that the initial flexural stiffness can be markedly improved with the hybrid strengthening method. However, the initial damage level had little influence on the final crack width. In addition, an analytical model was proposed to evaluate the flexural behaviors of the strengthened HCBs. The simulation results of the preload, ultimate load and failure modes agreed well with the experimental ones.

Structural behavior of hollow-core reinforced self-compacting concrete beams

This paper presents an experimental investigation on the structural performance of hollow-core reinforced self-compacting concrete beams and performs an optimization analysis to select the optimum hollow-core beam section, as well as perform a sustainability analysis. The experimental program includes constructing and testing five beams with different longitudinal hollow-core diameters created by using recycled plastic pipes, as well as a solid beam, used as a reference specimen. The results show that it can reduce the concrete from self-compacting concrete beams with percentages from 5.4 to 14.2 with a decrease in the first crack load from 9.1 to 22.7% and the ultimate strength from 2.3 to 10.5% respectively compared to the reference solid beam. The optimization analysis shows that the beam of 46 mm diameter hollow-core is the optimum selection in the concrete volume reduction of 11.1%, cracking load, and ultimate load reduction of 13.6% and 9.3% respectively among all the other beam specimens. While the sustainability analysis reveals that, using longitudinal voids of diameters from 32 to 52 mm leads to a decrease in the embodied energy with percentages from 5.4 to 14.2% and carbon dioxide emission with percentages from 5.4 to 14.1% respectively. Increasing the longitudinal void diameter makes hollow-core self-compacting concrete beams more ductile and exhibits large deflections before failure occurrences.Article HighlightsTests on hollow-core reinforced self-compacting concrete beams are conducted.Recycled plastic pipes are used to create hollow-core in the beams and to reduce ineffective concrete.Reducing ineffective concrete contributes to sustainability with maintaining a good ratio of beam strength.

Potential of Longitudinal Post-Tensioning for Short-to-Medium Span Timber Bridges

On the basis of recent developments in post-tensioned multi-storey timber buildings using un bonded tendons, this paper aimed at investigating the potential of implementing a similar technology for innovative solutions for timber bridges. In particular, several technological solutions are proposed for future development, using several different cross sections and longitudinal profiles suitable for short-to-medium bridge spans, with both internal and external longitudinal ten dons, in some cases supplemented by transverse post-tensioning. In addition, a feasibility study of a short-span timber bridge is presented, with longitudinally posttensioned laminated veneer lumber (LVL) hollow core beams as an alternative to the existing concrete solution. The discussion includes a comparison between newly proposed and traditional solutions based on the evaluation of long-term post-tensioning losses, a cost analysis and some considerations on sustainability issues.